Pseudo-second Order Kinetic Equation Research Articles

Characteristics and defluoridation performance of granular activated carbons coated with manganese oxides

Using a redox process, granular activated carbon (GAC) was coated with manganese oxides to enhance its ability to adsorb fluoride from an aqueous solution. Compared with plain GAC, the fluoride adsorption capacity of this new adsorbent was improved and at least three times greater than that of uncoated GAC. The surface characteristics of coated GAC were observed with scanning electron microscopy. The surface area of the new adsorbent was calculated using the Brunauer–Emmett–Teller method. X-ray diffraction revealed that manganese oxides are amorphous. X-ray photoelectron spectroscopy demonstrated that manganese existed primarily in the oxidation state +IV. Kinetic and equilibrium adsorption data showed that the adsorption process follows the pseudo-second order kinetic and Freundlich equation models. The sorption data also indicated that the removal of fluoride by adsorption is a highly complex process, involving both boundary layer diffusion and intra-particle diffusion. The pH value of solution influences fluoride removal, and the optimum equilibrium pH value of fluoride adsorption is 3.0.

Biosorption of Co(II) by immobilised Pleurotus ostreatus

Cobalt biosorption by Pleurotus ostreatus immobilised in calcium alginate has been studied. The experimental results showed that immobilised Pleurotus ostreatus were effective for removing Co(II) from aqueous solution. Co(II) biosorption equilibrium was approached within 120 min. Pseudo second-order kinetic equation was applicable to all the sorption data over the entire time range. Intra-particle diffusion was not the only rate-limiting step. The biosorption data conformed better to Langmuir Isotherm Model than Freundlich Isotherm Model. The maximum adsorption capacity (qm) onto Pleurotus ostreatus immobilised in calcium alginate was 13.5 mg/g for Co(II). The FT?IR analysis showed that the mechanism involved in biosorption of Co(II) by Pleurotus ostreatus was mainly attributed to binding of amide I group.

Sorption isotherm and kinetic modeling of aniline on Cr-bentonite

In this paper, the sorption characteristics of aniline on Cr-bentonite prepared using synthetic wastewater containing chromium was investigated in a batch system at 30 °C. The effects of relevant parameters, such as pH value of solution, adsorbent dosage and initial aniline concentration were examined. The experimental data were analyzed by the Langmuir and Freundlich, and Temkin models of sorption. The sorption isotherm data were fitted well to Langmuir isotherm and the monolayer sorption capacity was found to be 21.60 mg/g at 30 °C. Dubinin–Redushkevich (D–R) isotherm was applied to describe the nature of aniline uptake and it was found that it occurred chemically. The kinetic data obtained at different concentrations were analyzed using a pseudo first-order, pseudo second-order kinetic equation and intraparticle diffusion model. The experimental data fitted very well the pseudo second-order kinetic model. Intraparticle diffusion affects aniline uptake. The results indicate that there is significant potential for Cr-bentonite as an adsorbent material for aniline removal from aqueous solutions.

Removal of Methylene Blue from Aqueous Solution by Non-Living Biomass of Marine Algae and Freshwater Macrophyte

The adsorption of Methylene Blue, a Basic dye, onto the nonliving biomass of marine algae and freshwater macrophyte was investigated by batch experiments. Such adsorption onto both adsorbents was pH-independent. The experimental data were analyzed using pseudo-first-order and pseudosecond-order kinetic equations, the results suggesting that the data were described well by both models. Intraparticle diffusion played an important role in the mass-transfer process. Methylene Blue adsorption onto both adsorbents at 20°C was also evaluated by the Freundich and Langmuir isotherms. The maximum adsorption capacities were 155.31 mg/g for Laminaria japonica (LJ) biomass and 150.39 mg/g for alligator weed (AW) biomass, respectively. The effects of adsorbent concentration and ionic strength on Methylene Blue adsorption were also investigated. The adsorbents investigated could serve as low-cost adsorbents for removing Methylene Blue from aqueous solution.

Synthesis and Characterization of Amidoximated Polyacrylonitrile/Organobentonite Composite for Cu(II), Zn(II), and Cd(II) Adsorption from Aqueous Solutions and Industry Wastewaters

A new adsorbent, polyacrylonitrile/organobentonite composite with amidoxime functionality was prepared using in situ intercalation polymerization technique and characterized by Fourier transform infrared spectroscopy, X-ray diffraction pattern, scanning electron microscopy, surface area analyzer, thermogravimetry, and potentiometric analysis. The adsorption of Cu(II), Zn(II), and Cd(II) ions was examined by batch-equilibrium technique with respect to the initial pH, adsorbent dose, ionic strength, contact time, and initial metal concentration. Adsorption-complexation, in addition to ion exchange, must be involved in the sorption process. Maximum adsorption of 99.8% Cu(II), 98.9% Zn(II), and 97.4% Cd (II) with 2 g/L of the adsorbent was observed at pH 6.0 for an initial metal concentration of 25 mg/ L. The kinetic data were reasonably correlated with pseudosecond-order kinetic equation. An increase of ionic strength on the medium caused a decrease in metal adsorption, indicating the occurrence of outer-sphere surface complex mechanism for the metal. The equilibrium isotherm data were analyzed using Langmuir, Freundlich, and Scatchard isotherm models; however, the Langmuir model was found to provide the best correlation. The maximum monolayer adsorption capacity was 77.43, 65.40, and 52.61 mg/g for Cu(II), Zn(II), and Cd(II) ions, respectively, at 30 °C. The adsorption efficiency toward heavy metals removal was tested using different industry wastewaters. Acid regeneration was tried for several cycles with a view to recover the adsorbed metals and also to restore the adsorbent to its original state.

Kinetics and isotherms of Neutral Red adsorption on peanut husk

Adsorption of Neutral Red (NR) onto peanut husk in aqueous solutions was investigated at 295 K. Experiments were carried out as function of pH, adsorbent dosage, contact time, and initial concentration. The equilibrium adsorption data were analyzed by Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, and Toth isotherm models. The results indicated that the Toth and Langmuir models provided the best correlation of the experimental data. The adsorption capacity of peanut husk for the removal of NR was determined with the Langmuir and found to be 37.5 mg/g at 295 K. The adsorption kinetic data were modeled using the pseudo-first order, pseudo-second order, and intra-particle diffusion kinetic equations. It was seen that the pseudo-first order and pseudo-second order kinetic equations could describe the adsorption kinetics. The intraparticle diffusion model was also used to express the adsorption process at the two-step stage. It was implied that peanut husk may be suitable as adsorbent material for adsorption of NR from aqueous solutions.

Adsorption and removal of cadmium (II) from aqueous solutions by bio-formulation

A novel sorbent, bio-formulation(BF), was prepared and employed for the adsorption of cadmium(Cd) ion from aqueous system. The process of adsorption follows the pseudo second-order kinetic equation and the adsorption behavior is fitted with a Freundlich isotherm. The removal rate of Cd is slightly dependent on the initial pH value over a wide range of 4–11. The addition of Zn 2+ and Cu 2+ ions hardly affects the Cd adsorption, whereas the coexisting Pb 2+ ion greatly interferes with the adsorption. The adsorption mechanism is supposed as a cation-exchange process between Cd 2+ and calcium and Mg 2+ present on the surface of BF, and somewhat as adsorption in a hydrolyzed form. The adsorbed Cd ions are desorbed effectively by a 0.1 mol/L HCl solution.

Activated carbons for the adsorption of ibuprofen

Powdered activated carbons prepared from cork waste were studied for the ibuprofen removal from liquid phase. Two carbons were used: CAC obtained by chemical activation with K 2CO 3, and CPAC prepared by a two-step method, chemical activation with K 2CO 3 followed by steam activation. The ash content analysis showed that, for this raw material, the previous acid treatment can be omitted. The textural properties of the samples, evaluated by low temperature N 2 adsorption, show that the main difference is related with the volume of the larger micropores (supermicropores), which is more developed for CPAC. The surface chemistry characterization, made by the determination of the point of zero charge (PZC) and Boehm’s titration, show that the second activation step led to an activated carbon with less acidic groups, associated with the absence of the strongest acidic groups. Kinetic and equilibrium adsorption data show that the process obeys to the pseudo-second order kinetic equation and Langmuir adsorption model. Between 25 and 40 °C no significant influence of the temperature on ibuprofen adsorption was observed. Results indicate that the removal efficiency is higher than 90% between pH 2 and 4 and decreases as pH values increase to a value of 11. The results show that both samples are suitable for ibuprofen removal, although CPAC has advantages, namely, high initial adsorption rate, high adsorption capacity and high removal efficiency, in some cases 100%, for a large range of pH.

Elucidation of the naproxen sodium adsorption onto activated carbon prepared from waste apricot: Kinetic, equilibrium and thermodynamic characterization

In this study, activated carbon (WA11Zn5) was prepared from waste apricot, which is waste in apricot plants in Malatya, by chemical activation with ZnCl 2. BET surface area of activated carbon is determined as 1060 m 2/g. The ability of WA11Zn5, to remove naproxen sodium from effluent solutions by adsorption has been studied. Equilibrium isotherms for the adsorption of naproxen sodium on activated carbon were measured experimentally. Results were analyzed by the Langmiur, Freundlich equation using linearized correlation coefficient at 298 K. The characteristic parameters for each isotherm have been determined. Langmiur equation is found to best represent the equilibrium data for naproxen sodium–WA11Zn5 systems. The monolayer adsorption capacity of WA11Zn5 for naproxen sodium was found to be 106.38 mg/g at 298 K. The process was favorable and spontaneous. The kinetics of adsorption of naproxen sodium have been discussed using three kinetic models, i.e., the pseudo first-order model, the pseudo second-order model, the intraparticle diffusion model. Kinetic parameters and correlation coefficients were determined. It was shown that the pseudo second-order kinetic equation could describe the adsorption kinetics for naproxen sodium onto WA11Zn5. The thermodynamic parameters, such as Δ G°, Δ S° and Δ H°, were calculated. The thermodynamics of naproxen sodium–WA11Zn5 system indicates endothermic process.

Comment on “Kinetics of Solute Adsorption at Solid/Solution Interfaces: A Theoretical Development of the Empirical Pseudo-First and Pseudo-Second Order Kinetic Rate Equations, Based on Applying the Statistical Rate Theory of Interfacial Transport”

Comment on “Kinetics of Solute Adsorption at Solid/Solution Interfaces: A Theoretical Development of the Empirical Pseudo-First and Pseudo-Second Order Kinetic Rate Equations, Based on Applying the Statistical Rate Theory of Interfacial Transport”

Reply to “Comment on “Kinetics of Solute Adsorption at Solid/Solution Interfaces: A Theoretical Development of the Empirical Pseudo-First and Pseudo-Second Order Kinetic Rate Equations, Based on Applying the Statistical Rate Theory of Interfacial Transport”

Reply to “Comment on “Kinetics of Solute Adsorption at Solid/Solution Interfaces: A Theoretical Development of the Empirical Pseudo-First and Pseudo-Second Order Kinetic Rate Equations, Based on Applying the Statistical Rate Theory of Interfacial Transport”

Kinetics of Solute Adsorption at Solid/Solution Interfaces: A Theoretical Development of the Empirical Pseudo-First and Pseudo-Second Order Kinetic Rate Equations, Based on Applying the Statistical Rate Theory of Interfacial Transport

For practical applications of solid/solution adsorption processes, the kinetics of these processes is at least as much essential as their features at equilibrium. Meanwhile, the general understanding of this kinetics and its corresponding theoretical description are far behind the understanding and the level of theoretical interpretation of adsorption equilibria in these systems. The Lagergren empirical equation proposed at the end of 19th century to describe the kinetics of solute sorption at the solid/solution interfaces has been the most widely used kinetic equation until now. This equation has also been called the pseudo-first order kinetic equation because it was intuitively associated with the model of one-site occupancy adsorption kinetics governed by the rate of surface reaction. More recently, its generalization for the two-sites-occupancy adsorption was proposed and called the pseudo-second-order kinetic equation. However, the general use and the wide applicability of these empirical equations during more than one century have not resulted in a corresponding fundamental search for their theoretical origin. Here the first theoretical development of these equations is proposed, based on applying the new fundamental approach to kinetics of interfacial transport called the Statistical Rate Theory. It is shown that these empirical equations are simplified forms of a more general equation developed here, for the case when the adsorption kinetics is governed by the rate of surface reactions. The features of that general equation are shown by presenting exhaustive model investigations, and the applicability of that equation is tested by presenting a quantitative analysis of some experimental data reported in the literature.

Carbonate effects and pH-dependence of uranium sorption onto bacteriogenic iron oxides: Kinetic and equilibrium studies

The removal of U(VI) from groundwaters by adsorption onto bacteriogenic iron oxides (BIOS) has been investigated under batch mode. The adsorbent dosage, the uranium concentration, the concentration of carbonate and the use of a real groundwater spiked with uranium comprised the examined parameters. In addition, the effect of pH was examined in two different water matrixes, i.e., in distilled water and in real groundwater. Equilibrium studies were carried out to determine the maximum adsorption capacity of BIOS and the data correlated well with the Langmuir and Freundlich models. The presence of carbonate affected adversely the adsorption of U(VI) onto BIOS. The maximum adsorption capacity of BIOS was 9.25 mg g −1 at 0.1 mM carbonate concentration and decreased to 6.93 mg g −1 at 0.5 mM carbonate concentration, whereas at carbonate concentration of 2 mM practically no adsorption occurred. The data were further analyzed using the pseudo-second order kinetic equation, which fitted best the experimental results. The initial adsorption rate ( h) was found to increase with decreasing the concentration of carbonate in all cases. When experiments were accomplished in the absence of carbonate, the pH values did not have an effect on the adsorption of U(VI). However, the extent of U(VI) adsorption was strongly pH-dependent when the experiments were carried out in the real groundwater. The maximum adsorption capacity increased sharply as the pH decreased and optimum removal was obtained in the pH range 3.2–4.0, thus bacteriogenic iron oxides can found application in the removal of U(VI) by adsorption from low pH or low carbonate waters.

Kinetic study of immobilized lysozyme on the extrudate-shaped NaY zeolite

The adsorption rate of lysozyme onto the extrudate-shaped NaY zeolite was studied in a reciprocal shaking water bath system and shown to be a function of shaking rate, initial lysozyme concentration, and operating temperature. The initial adsorption rate was mainly dependent on the shaking rate and the equilibrium of adsorption for lysozyme was approached after 30 min. The saturation capacity was found to be 16.43 (mg lysozyme/g zeolite) for an increase in the shaking rate up to 150 rpm. The initial rates increased from 1.987 to 6.260 (mg lysozyme/min g zeolite) with increasing the initial lysozyme concentration from 0.25 to 2.0 (mg lysozyme/ml solution). However, the initial adsorption rate decreased with an increase in temperature. The values of saturation capacity for lysozyme of the zeolite significantly decreased from 35.21 to 14.92 (mg lysozyme/g zeolite) with temperature increasing from 277 to 310 K. Furthermore, the experimental data were analyzed using various kinetic models (i.e. KEKAM, pseudo-first order, and pseudo-second order) to determine the best-fit equation for describing the adsorption behavior. The results showed that the pseudo-second order kinetic equation was the most appropriate to predict the dynamic adsorption behavior of lysozyme on the zeolite. This suggested that the rate-controlling step might be the surface reaction mechanism but not the mass transport to the external surface of the zeolite. Additionally, desorption rate of the immobilized lysozyme on the zeolite in the presence of 1.0 M NaCl was measured at different temperatures (277–310 K). One proposed model was used to predict the experimental desorption data for the elution of the adsorbed lysozyme. The kinetic parameters and activation energy of the desorption process were also determined.

Cinética e equilíbrio de adsorção dos oxiânions Cr (VI), Mo (VI) e Se (VI) pelo sal de amônio quaternário de quitosana

O sal quaternário de quitosana foi sintetizado com cloreto de glicidil trimetil amônio. A modificação química foi caracterizada por espectrometria no IV, RMN de 13C e ¹H, e mmol/g de grupos quaternários presentes na matriz polimérica por condutimetria. A remoção de Cr (VI), Mo (VI) e Se (VI), em meio aquoso, foi investigada em processo de batelada. A adsorção mostrou ser dependente do pH para o Cr (VI) e Se (VI), com um pH ótimo de adsorção, entre 4,0 a 6,0. Para o Mo (VI) a adsorção manteve-se quase constante no intervalo de pH entre 4,0 e 11,5. O modelo de isoterma de Langmuir descreveu melhor os dados de equilíbrio na faixa de concentração investigada. No presente estudo, um grama do sal quaternário de quitosana reticulado com glutaraldeído adsorveu 68,3 mg de Cr, 63,4 mg de Mo e 90,0 mg de Se. A velocidade de adsorção, no processo, segue a equação cinética de pseudo segunda-ordem, sendo que o equilíbrio para os três íons foi alcançado próximo aos 200 minutos. A análise dispersiva de raios-X para o Cr (VI) mostrou que o principal mecanismo de adsorção é a troca iônica entre os íons Cl- da superfície do polímero pelos oxiânions. O trocador aniônico apresentou a seguinte ordem de seletividade: Cr (VI) > Mo (VI) > Se (VI).